// 通过css预处理器的函数方法，实现伪类线
border-1px($color)
    position: relative
    &:before
      display: block
      position: absolute
      left:0
      top: 0
      width: 100%
      border-bottom: 1px solid $color
      content: ''
    &:after
      display: block
      position: absolute
      left:0
      bottom: 0
      width: 100%
      border-top: 1px solid $color
      content: ''

border-none()
    &:before
      display: none
    &:after
      display: none



//插入图片
bg-image($url)
    background-image: url($url+"@2x.png")
    @media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3)
      background-image: url($url+"@3x.png")